Premise: Adult story based on children's storybook Alexander and the Terrible, Horrible, No Good, Very Bad Day by Judith Viorst.
Path 1: Comedic along the lines of Jim Carrey meets George Carlin.
Path 2: Dr Jeckyl and Mr Hyde along the lines of the movie Falling Down or any similar scenario where a good guy has just had enough and finally snaps. No special background to the guy ie not ex military or hitman or anything similar.... no violence in his past at all... but once he snaps, he goes intensely feral and vicious.